Method of treating rubber-reinforcing material



'and the reinforced rubber.

United States Patent METHOD OF TREATING RUBBER-REINFORCING The presentinvention relates to methods of treating rubber-products-reinforcingfibrous material for improving physical properties such astensile-strength, heat resistance, fatigue resistance and adhesionproperties of the rubber products at ordinary temperature and underexothermic conditions.

In many cases, fibrous material which is to serve as a rubberreinforcement is required to have substantial resistances to heat, Waterand fatigue. Particularly in major rubber products such as automobiletires and conveyer belts, resistances to heat, Water and fatigue arecritical, and the performance of such products, in fact, largely dependsupon such characteristic properties, as is well known in the art.Resistances to heat, Water and fatigue are required for both fibrousreinforcing material per se and for the adhesive bonds between suchmaterial In other words, fibrous rubber-reinforcing material forindustrial use not only must have itself substantial resistances toheat, water and fatigue but also must have a substantial adhesivestrength with respect to the rubber reinforced by the fibrous material.In addition, such adhesion is required to be heatand Water-resistant aswell as dynamically resistant to fatigue load.

An object of the present invention is to provide a method of treatingfibrous rubber-reinforcing material for enhancing the strength of thematerial per se as Well as the adhesive strength thereof with respect torubber material. According to the present invention, there is provided amethod of treating fibrous material adapted for the reinforcement ofrubber products such as tires, belts or hoses, for example, natural orsynthetic fibrous material in the form of tire cords or belt duckcharacterized by the immersion of such material in a dilute solution,dispersion or emulsion of drying oil or semidrying oil essentiallycomprised of fatty acid glycerides containing metal soap as describedhereinafter. This method, it has been found, imparts to the fibrousmaterial substantial resistances to water and heat, as well asflexibility and improved adhesive strengths under heated conditions andresistance to fatigue load.

The diluted treating composition of drying oil or semidrying oilprincipally comprised of fatty acid glycerides including metal soap is,according to the present invention, either a dilute solution thereof inan organic solvent having a concentration of not more than 10%, butpreferably not more than 5%, or a dilute emulsion of such oil dispersedand emulsified in water having a concentration of not more than orpreferably not more than 5%.

According to the present invention, the application of such treatingcomposition onto fibrous material may be effected at the spinning stage,or application may be effected or may be performed after the spinningstage upon fibrous material in the form of yarns, cords or fabrics.Application may also be effected by employing an RFL(resorcin-formalin-latex) solution to which is added the treatingcomposition for the adhesive treatment of the cords or fabrics thismethod comprising immersing such cords or fabrics in the mixture orspreading the latter over such cords or fabrics. In either case, theapplication of such treating compositionis performed 3,135,624 PatentedJune 2, 1964 ICC during or immediately before or after the adhesivetreatment.

In case the treatment of fibers is effected at the spinning stage, suchtreatment is effected either by incorporating the treating compositioninto the finishing agent used at the step of oiling, or it is effectedbefore or after the usual oiling process.

The metal soap contained in the treating composition according to thepresent invention has the general formula [CH -(CH -CO Me, and a meltingpoint of C. or under. In this formula, Me is a divalent 'metal, and n isa positive integer of 8 to 18.

In the treatment of fibrous material with such metal soap, the metalsoap is compounded with a drying oil or semidrying oil, the proportionof the metal soap to the drying or semidrying oil being 50% or less. Thedrying oil or semidrying oil compounded with the metal soap is dissolvedin an organic solvent to form a dilute solution having a concentrationof 10% or less. An alternative method of preparing such dilute solutionis to disperse the drying or semidrying oil added with the metal soap inwater to form a water emulsion having a concentration of 10% or less.The dilute solution thus prepared of drying or semidrying oil containingmetal soap should have a concentration of 10% or less, or preferably 5%or less.

This treatment of fibrous material according to the present invention ispreferably effected so that the fibrous material after immersiontreatment have a solids pick-up'of under 5% by weight of the fibrousmaterial.

The fibrous material thus treated, when used as a I rubber-reinforcingmaterial, exhibits itself striking improvements in water resistance,flexibility, and heatand fatigue-resistances, the adhesive bond formedbetween the fibrous and rubber materials also exhibiting improvedresistances to heat, water and fatigue thereby securing a satisfactoryadhesion between the two materials.

Many of major rubber products such as tires, rubber belts and rubberhoses comprise a combination of rubber and fibrous material as areinforcement therefor, the effective service life of such productsdepending on the performances of the reinforcing material used and theadhesive bond formed between the rubber and the reinforcing material.

The method of treating rubber-reinforcing material in accordance withthe present invention, in effect, extends the service life of rubberproducts reinforced by the material and improves the qualities thereof,and this is evident from the results of laboratory researches and practical tests performed by the inventors.

A number of practical examples will now be specifically described.

EXAMPLE 1 The method of the present invention was applied tohigh-tenacity rayon while it was being spun into yarns of 1650 D. Oilingis generally used in spinning ordinary high-tenacity rayon yarns of 1650D. Good results were obtained by replacing part or all of the commontire cord oil used in such oiling by a dilute solution of drying orsemidrying oil admixed with metal soap in accordance with the presentinvention. In this example, 70 parts of the oil was replaced by the oilpreparation according to the present invention. The metal soap used wascadmium stearate, and the vegetable oil was soy bean oil which is adrying oil. The compounding ratio of the diluted liquid composition usedwas as follows:

6% water emulsion used: Parts Water dispersion of Cd-stearate 20.00Water 70.00 Soy bean oil 10.00

A 6% water emulsion containing 2% of Cd-stearate and 4% of soy bean oil.

Dimol N: Partially desulfonated Na ligno sulphonate. 2 Aerosol OT Sodiumdioctyl sulfosuecinate.

A water dispersion of Cd-stearate.

Water emulsion of soy bean oil: Parts Soy bean oil 4.0 Casein 0.1 NH OH0.1 Water 5.8

A 40% water dispersion of soy bean oil.

Firstly, a water dispersion of Cd-stearate was prepared. The quantity ofwater as defined above was heated to about 50 to 60 C., and then AerosolOT, Dirnol N and sodium alginate were successively added to anddissolved in the water with stirring. After cooling the resultantsolution to the room temperature, Cd-stearate was gradually admixed tothe solution with stirring to form a homo geneous mixture. This mixturewas subjected to the action of a ball mill for to 24 hours to give a 10%water dispersion of Cd-stearate.

A water emulsion of soy bean oil was separately prepared. The amount ofwater as specified in the above recipe was heated to about 60 to 70 C.After 28% aqueous ammonia and casein were completely dissolved in theheated water with stirring, soy bean oil was gradually added whileagitating the solution. Then, the mixture was homogeneously dispersed bya homogenizer to form a 40% water emulsion of soy bean oil.

70 parts of water was added with stirring to parts of the prepared waterdispersion of Cd-stearate to form a complete mixture. To this, 10 partsof 40% emulsion of soy bean oil was added with stirring and the mixturewas passed once through a homogenizer to complete the preparation of theinventive treating composition. In this example, 6% water emulsioncontaining 2% of metal soap and 4% of vegetable oil was used.

The 6% emulsion thus prepared (containing Cd-stearate 2% and soy beanoil 4%) was mixed with usual tire cord oil in a proportion such thatabout 70% of the solids con tent in the oil preparation is formed of thesolid ingredicnts of the treating composition prepared according to thepresent invention. In this example, 3% oil preparation was formed whichcontained per litre 9 grams of tire cord oil and 21 grams of thetreating agent according to the present invention, and was used foroiling" in spinning high-tenacity rayon yarns of 1650 D. After oiling,the spun yarns were dried and wound up in the usual manner. The yarnsthus treated exhibited remarkably improved waterand heat-resistance. Theyarns were used to form tire cords of 1650 D/ 2 and 12 turns per inchboth in upper and lower twist, which cords exhibited very excellentresistances to heat, water and fatigue as compared to those notsubjected to the treatment of the present invention. The cords werefurther treated with resorcinformalin-latex in the usual manner and theadhesive characteristics of the cords thus treated were determined. Theresults include many noteworthy figures as follows, showing that theheatand water-resistant adhesive strengths were highly improved by thetreatment.

Test Data of Example 1 Prior Present method, method, kg. kg.

Raw cord strength (bone dry) 13. 5 14.1 Strength of cord dipped in RFL(bone dry) 13. 9 14.5 Strength after heating for 5 hours at 165 C... 10.3 13.2 Strength after heating for 10 hours at 165 C 9. 4 11.2 Adhesivestrength of cord (II-test):

After heating for 1 hour at C 11.0 11.7 After heating for 1 hour at 160C 6. 8 7. 6 After dipping in water for 24 hours 4. 4 5. 5

As clearly seen in the data, in this example, the tire cords exhibitedexcellent heat-resistant strengths and improved adhesive characteristicsparticularly under heated conditions.

The cords treated were further employed to form automobile tires whichexhibited excellent performances.

Tires of the type 825-20-14 PR (12P) were prepared with the tire cordstreated in accordance with this invention and subjected to indoorrunning tests under the following conditions: Speed, 40 miles/ hr. airpressure, TRA std; load, of TRA std and 10% up for each additional 250miles.

The running life distance obtained was about 3800 km., which is about40% up as compared with ordinary 825- 2014 PR (12?) tires, which had2700 km. life. In the indoor running test on the tire which was builtusing the cords treated according to this invention, the growth of outercircumference and Width and heat generation in the tire were much lessthan those of the ordinary tire. These facts represent a remarkableimprovement in tire qualities realized by the improvements in variousproperties of the tire cords as described above, demonstrating thesuccessful effects of the present invention.

EXAMPLE 2 Immediately before the adhesive treatment of tirecords, themethod of the present invention was applied thereto. The tire cordfabrics were preliminarily immersed in the diluted liquid composition ofvegetable oil containing metal soap according to the present invention,dried and immediately subjected to the so-called tire cord dipping(resorcin-formalin-latex treatment).

The metal soap used in this example was zinc stearate, and the vegetableoil was cotton seed oil which is a semi drying oil, the diluent being anorganic solvent. The treating process was as follows: Zinc stearate wasdispersed in a mixed solvent of CCL; and methyl alcohol in proportion of3 to 1 to give the Zn stearate content of 2.5%. Then, cotton seed oilwas added with stirring to obtain a 5% solution of cotton seed oil. Theresultant dilute solution thus contained 5% of cotton seed oil and 2.5%of zinc stearate. Tire cords were immersed in this treating solutionbefore the usual dipping step. That is, the tire cord fabrics werepreliminarily dipped in the treating solution of the present inventionwith the cords held in light tension. After removing any excess of thesolution thus applied to the fabrics by means of a squeeze roll, thefabrics were dried so that the cords had a water content of 15% or less,or preferably 5% or less. In

ing such cords also exhibited an extended running life. After the indoorrunning test of 1000 km., the tire was cut and tested for cord andadhesive strengths, which showed remarkable improvements as follows:

Prior Present 1650 D/2 high-tenacity rayon cord method, method,

kg. kg.

Strength of cord (bone dry) 14.1 15.0 Strength after heating for 5 hoursat 165 0... 11.4 13. 5 Strength after heating for hours at 165 C 9i 711.5 Strength after 1,000 km. indoor running test 12. 7 13. 7 Cordadhesive strength (H-test):

After heating for 1 hour at 130 C 10. 5 11.0 After heating for 1 hour at160 C" 7.0 7. 7 After immersion in water for 24 hours 4. 3 5.0 Adhesivestrength:

After 1,000 km. indoor running test 1 19. 2 26. 2

1 Peeling between 9th and 10th plies in tire type 825- 14 PR (121 Asapparent from the foregoing description of typical practical exampleswhere rayon tire cords were sub-' jected to the reinforcing treatmentaccording to the present invention, the cords treated according to thepresent invention exhibited improved resistances to heat, water andfatigue as well as improved adhesion resistances, rubber tires employingsuch cords having an extended service life and improved performances.

It will be understood that the industrial fibrous materials which may betreated according to the present invention are not limited to rayon tirecords but also includes other industrial synthetic fibrous materialssuch as rayon belt duck, nylon cords and nylon duck.

It will also be understood that, though, in the examples, typicallydrying or semidrying oil was used for containing metal soap, any of thevegetable oils or any combination thereof may also be used.

In order to apply a dilute solution of vegetable fat or oil containingmetal soap to fibrous material, various processes may be employed asstated hereinbefore; that is, the application may be effected on fibersat the spinning stage, or on yarns, cords or fabrics after spinning, orby immersing such cords or fabrics in an adhesive solution or spreadingsuch solution thereover at the time of adhesive treatment with thedilute solution admixed to the adhesive solution. Alternatively, thismay be effected after or before the adhesive treatment.

What is claimed is:

l. A method of treating a fibrous rubber reinforcing material in orderto improve its physical properties, particularly its heat resistance andbonding to the rubber material, which method comprises immersing therubber reinforcing material in a dilute solution of a vegetable oilcontaining a metal soap having the general formula wherein Me representsa divalent metal and n represents a positive integer between 8 and 18,drying the reinforcing material after withdrawal from the solution andthen subjecting it to an adhesive treatment with aresorcinformaldehyde-resin.

2. A method as defined in claim 1 wherein the solvent for the vegetableoil is water.

3. A method as defined in claim 1 wherein the solvent for the vegetableoil is an organic solvent.

4. A method of treating a fibrous rubber reinforcing material in orderto improve its physical properties, particularly its heat resistance andbonding to the rubber material, which method comprises immersing therubber reinforcing material in a dilute solution of a vegetable oilcontaining a metal soap having the general formula wherein Me representsa divalent metal and n represents a positive integer between 8 and 18 soas to incorporate in the said reinforcing material a solids contentobtained from said vegetable oil and metal soap in an amount of up to 5%by weight of the reinforcing material, said metal soap being applied tosaid fibrous material at a time distinct from the application to saidfibrous material of a resorcin-formaldehyde-resin.

5. A method of treating a fibrous rubber reinforcing material in orderto improve its physical properties, particularly its heat resistance andbonding to the rubber material, which method comprises immersing thereinforcing material in a mixture of a dilute solution of vegetable oilcontaining a metal soap having the general formula wherein Me representsa divalent metal and n represents a positive integer between 8 and 18,and a solution of a bonding agent, and drying the reinforcing materialafter Withdrawal from said mixture of solutions.

6. A method of making rubber products which are reinforced with anindustrial fibrous material, said method comprising immersing thefibrous material in a dilute solution of a vegetable oil containing ametal soap having the general formula [CH (CH CO Me Me being a divalentmetal, n being a positive integer between 8 and 18, after treating thefibrous material with a resorcin-formalin-resin, to improve the physicalproperties, the heat resistance and the bonding strength, of the rubberproducts.

7. A method of making rubber products which are reinforced with anindustrial fibrous material, said method comprising immersing thefibrous material in a dilute solution of a vegetable oil containing ametal soap having the general formula wherein Me represents a divalentmetal and n represents a positive integer between 8 and 18.

References Cited in the file of this patent UNITED STATES PATENTS1,807,755 Ryley et al. June 2, 1931 2,431,078 Powell et al. Nov. 18,1947 2,436,980 Standley et al. May 2, 1948 2,663,653 Zimmerman Dec. 22,1953 2,673,818 Woog Mar. 30, 1954 2,869,610 Lippman et al Jan. 20, 1959

1. A METHOD OF TREATING A FIBROUS RUBBER REINFORCING MATERIAL IN ORDERTO IMPROVE ITS PHYSICAL PROPERTIES, PARTICULARLY ITS HEAT RESISTANCE ANDBONDING TO THE RUBBER MATERIAL, WHICH METHOD COMPRISES IMMERSING THERUBBER REINFORCING MATERIAL IN A DILUTE SOLUTION OF A VEGETABLE OILCONTAINING A METAL SOAP HAVING THE GENERAL FORMULA